Air screens



E. F. GYGAX AIR SCREENS Feb. 1, 1966 2 Sheets-Sheet 1 Filed June 21, 1965 Z@ INVENTOR ad F s??? BY ATT'Y Feb. 1, 1966 Filed June 21, 1965 E. F. GYGAX AIR SCREENS 2 Sheets-Sheet 2 INVENTOR.

ATT'Y United States Patent O 3,232,204 AIR SCREENS Ernest F. Gygax, Glendale, Mo., assignor to Universal Match Corporation, Ferguson, Mo., a corporation of Delaware Filed June 21, 1963, Ser. No. 289,576 8 Claims. (Cl. 98-36) This invention relates to improvements in air screens. More particularly, this invention relates to improvements in devices which can establish and maintain air screens adjacent doorways.

It is, therefore, an object of the present invention to provide an improved device which can establish and maintain an air screen adjacent a doorway.

This invention is an improvement upon the invention disclosed and described in Steiner Patent No. 2,863,373 for `Device For Producing A Room-Closing Air Curtain which was granted December 9, 1958.

A device which can establish and maintain an .air screen adjacent a doorway usually includes a plenum chamber, an air disch-arge assembly adjacent the outlet of that plenum chamber, an air-intake chamber, a return `air duct, and an airmoving device that causes air to enter the plenum chamber, to pass outwardly through the air discharge assembly, to pass across the doorway, to enter the air-intake chamber, and then to pass through the return air duct to the plenum chamber. Devices of that type are eminently practical and highly satisfactory; and they `are being installed in progressively increasing numbers.

In some instances, the space immediately adjacent a doorway of a building is occupied by essential and critical `structural members of that building; and, in those instances, the plenum chamber may have to be given a size and a shape other than the optimum size and shape. Also, in those instances, the disposition and direction of the return air duct may have to be other than the optimum disposition and direction. As Ia result, in those instances, less than optimum performance of the device for establishing and maintaining air screens usually results. It would be desirable to provide a device for producing air screens which could provide optimum operation-even in those instances where the size and shape of the plenum chamber and the disposition and direction of the return air duct were other than optimum. The present invention provides such a device for producing air screens; and it does so by providing an air-diusing member immediately -adjacent the inlet face of the air dischargel assembly. That air-'diffusing member has a large number of openings therein; and those openings have venturi-like configurations. As the air `leaves the openings of that air-diffusing member,"that air experiences lan expansion in volume, a reduction in velocity, and a reduction in density; and, immediately thereafter, that air enters the air discharge assembly. In experiencing the said expansion in volume, the said reduction in density yand the said reduction in velocity, the air substantially loses all laterally-directed components of moti-on.l Consequently, that air is particularly Well adapted to issue smoothly and uniformly from the air discharge assembly in the intended direction. In this way, optimum operation of the device, for establishing and maintaining an air screen, is assured-even though the air which enters the plenum chamber of that device may have substantial laterally-directed motion. It is, therefore, an object of the present invention to provide an Iair-diffusing member immediately adjacent the inlet face of an air discharge assembly for a device for establishing and maintaining .air screens, and to equip that airdiifusing member with a number of openings which have venturi-like configurations.

In one preferred embodiment of the present invention, the air-diffusing member rests upon and moves with the 3,232,204 Patented Feb. 1, 1966 ICC inlet face of the air discharge assembly of the device for establishing and maintaining an air screen. Such an arrangement is desirable because it minimizes turbulence, and it also minimizes flutter in the air-directing members of the air discharge assembly. It is, therefore, an object of the present invention to mount an air-diffusing member so it rests upon and moves with the inlet face of an air discharge assembly of a device which establishes and maintains an air screen adjacent a doorway.

Other and further objects and advantages of the present invention should become apparent from an examination of the drawing and accompanying description.

In the drawing and accompanying description, a preferred embodiment of the present invention is shown and described; but it is to be understood that the drawing and accompanying description are for the purpose of illustration only and do not limit the invention and that the invention will be defined by the appended claims.

In the drawing, FIG. 1 is .a plan view of a small air discharge assembly and of an air-diffusing member for a device for producing an air screen.

FIG. 2 is a partially broken-away side elevational view of the air discharge assembly and air-diffusing member shown in FIG. l,

FIG. 3 is a plan view, on a large-r scale, of a portion of the air-diffusing member of FIG. 1,

FIG. 4 is a vertical section, on the scale of FIG. 3, through the air-diffusing member of FIG. 3, and

FIG. 5 is a partially-sectioned, schematic View of a device for producing air screens which utilizes the air discharge assembly 'and air-diffusing member rof FIGS. 1 and 2.

Referring to the drawing in detail, the numeral 10 denotes a plenum chamber for a device that can establish and maintain an air screen. That plenum chamber is disposed at the top of a doorway which is generally denoted by the numeral 14. An air intake chamber 16 is disposed at the bottom of that doorway; and la grating 18 serves as a porous supporting surface for pedestrians and vehicles passing through said doorway. A blower 11 has the intake thereof connected to the air-intake chamber 16; and it has the outlet thereof connected to the plenum chamber 10 by a return air duct 12. The rotor of the blower 11 will be driven by a suitable source of power, not sho'wn, such as an electric motor.

The numeral 24 denotes the frame of an air discharge assembly which is mounted in the outlet opening of the plenum chamber 10. A number of pivots 28 are mounted in the frame 24; Iand those pivots rotatably support a number of guide members 23 so those guide members can be tilted relative to that frame. An indicated particularly by FIG. 2, the guide members 23 are generally triangular in cross section and have plane portions 25 extending upwardly from the apices thereof.

The numeral 30 denotes pivots which are carried by the guide members 23; and those pivots project outwardly beyond the ends of those pivots project outwardly beyond the ends of those guide members. Connecting rods 26 have openings therein which telescope over the projecting ends of the pivots 30; and those connecting rods cause all of the guide members 23 to tilt in unison. A link 34 has an opening in the lower end thereof which telescopes over one of the pivots 28, has an opening adjacent the center thereof which telescopes over one of the pivots 30, and has an opening in the u-pper end thereof. The upper end of that link extends upwardly a considerable distance above the upper edges of the plane portions 25 of the guide members 23. A rod 36 has one end thereof connected to the opening in the upper end of the link 34; and that rod has the other end thereof connected to a servo motor 8, all as indicated by FIG. 5.

A short bar 38 extends upwardly from the plane portion 25 of the left-handmost guide member 23 in FIGS. 1 and 2; and the lower end of that bar is suitably secured to that plane portion, as by rivets. Similarly, a short bar 40 extends Iup-wardly from the plane portion 25 of the right-handmost guide member 23 in FIGS. 1 and 2; and the lower portion of that bar is suitably secured to that plane portion, as by rivets.

The numeral 42 generally denotes an air-diiusing member which is fused with the air discharge assembly of the present invention. As indicated particularly by FIGS. 1 and 3, that air diffusing member has a large number of vertically-directed circula-r openings 44 therein; and those openings are arranged in parallel rows. Moreover, the openings 44 in alternate rows are staggered relative to each other. As a result, the air diffusing member 42 provides a high degree or" porosity, and can permit substantial quantities of air to tiow through it.

As indicated particularly by FIGS. 3 and 4, each of the openings 44 of the air diff-using member 42 has a portion 46 of reduced diameter. That portion is located approximately half-way between the upper and lower surfaces of that air diffusing member. The openings 44 are tubular in nature, and lthe portions 46 of reduced diameter provide those openings with venturi-like configurations.

The bars 38 and 40 are dimensioned so they can telescope upwardly through two of the openings 44 in the air diffusing member 42. Whenever those two openings telescope downwardly over the bars 38 and 4t?, the under surface of the air diffusing member will rest upon, and be supported by, the upper edges of the plane portions 25 of the guide members 23. Those upper edges constitute the inlet face of the air discharge assembly; and hence the air diffusing member 42 is mounted at that inlet face. Where the guide members 23 are quite long, they can occasionally experience liutter; but the engagement of the air diffusing member 42 with the upper edges of the plane portions 2S of those guide members substantially completely prevents utterf Where desired, elongated bars 4S can be mounted within the frame 24 below the level of the bottoms of the guide members 23. Those bars are set parallel to the direction of traffic through the doorway 14; and they provide an ornamental appearance for the bottom of the air discharge assembly.

Also where desired, arcuate shields 50' can be secured to the left-hand face of the left-handmost guide member 23 and to the right-hand face of the right-handmost guide member 23. Those shields will project outwardly beyond the edges of the frame 24, and will largely keepl air from moving downwardly between that frame and the adjacent faces of the left-handmost and right-handmost guide members 23.

In the operation of the device, for establishing and maintaining an air screen, which is provided by the present invention, the blower 11 causes air to be drawn downwardly through the ,grating 1S into the air-intake chamber 16 and forces that air upwardly through the return air duct 12 into the plenum chamber 10i. That air can, depending upon the size and shape of the plenum chamber iti and the disposition and direction of the return air duct 12, have substantially :horizontally-directed com-i ponents of movement. The air entering the plenum chamber will establish a positive pressure within that plenum chamber; and that air will respond to that positive pressure to successively move downwardly through the openings 44 in the diiuser 42, between the guide -rnembers 23, past the bars 4S, whenever those bars are provided, and into the doorway 14. That air will have su'lcient velocity to .pass to the air inlet chamber 16; and the guide members 23 will cause that air to move in the desired direction.

The servo motor 8 can be suitably actuated to push or pull on the rod 36, and can thus cause the link 34 to rotate the guide members 23 in the counter clockwise direction or in the clockwise direction in FIG. 2. If the giide members 23 are caused to rotate in the counter clockwise direction, they will'cause the air which passes between them to incline downwardly from flipper left to lower right. On the other hand, if those guide members are moved in the clockwise direction, they will cause the air passing between them to incline downwardly yfrom upper right to lower left. When the guide members 23 are left in the .position shown by FlG. 2, they will cause the air passing between them to move directly downwardly toward the grating 18. The servo motor S can be actuated in a number of ways, but it will preferably be actuated in the manner disclosed in Letters Patent No. 3,092,008 for Air Screens which was granted June 4, 1963.

As the air passes downwardly through the air diffusing member 42, it will attain its maximum velocity and density and will have its minimum volume as it passes through the small diameter portions 46 of the openings 44. As that air moves downwardly below those small diameter portions, it will experience an increase in volume, a reduction in density, and a reduction in velocity. In passing downwardly through the air diffusing member 42, the air will largely lose any laterally-directed components of movement; and hence that air will be particularly well adapted to ilow in the direction set -by the guide member 23 of the air discharge assemby. Also, in passing downwardly through the air diffusing member 42, the air will be ditused with minimal turbulence. Consequently, the present invention can provide smooth and eiicient operation of the device for establishing and maintaining an air screen.

In the event the servo motor 8 acts through the rod 36 and the link 34 to tilt the guide members 23 relative to the pivots 2S, the bars 38 and 4G will cause the air diffusing member 42 to move with the upper edges of the plane portions 25 of the guide members 23. This is desirable because it prevents relative movement between those upper edges and the openings 44 in that air diffusing member.

If desired, the air didusing member 42 could be mounted above and out of engagement with the air discharge assembly. However, where that was done, a special supporting frame would have to .be provided for that air diffusing member. Furthermore, where the air diffusing member 42 is mounted above and out of engagement with the air discharge assembly, relative movement will occur between the upper edges of the plane portions 25 of the guide members 23 and the bottom face of that air diffusing member.

The venturi-like conguration of the openingsl 44 in the air diffusing member 42 enables that air diffusing member to provide an action which other air diffusing members can not provide. Specifically, that venturi-like configuration enables the air-diffusing member 42 to cause the air passing through that air diffusing member to langely lose any laterally-directed components of movement; and air diffusing members of the egg crate type can not cause the air passing through them to largely lose any laterally-directed components of movement. Also, that Venturi-like configuration enables the air-diffusing member 42 to minimize turbulence in the air passing through that air diffusing member; and air diffusing members of the egg crate type can not minimize turbulence in the air passing through them.

The portions 46 of reduced diameter of the air diffusing member 42 are defined by a thin plastic sheet, and those portions can be enlarged to some extent. That fact is important because it facilitates balancing of the flow of fthe air from the plenum ohlamber 10. Specifically, after the air discharge assembly has been mounted in the outlet opening of the plenuim chamber 1t), and after the blower 11 has been started, air flow measurements may show that too little air is flowing through some `areas of the air difusing member 42. When .that happens a long rod, with a diameter larger than the diameter of the openings 44, is forced upwardly bet-Ween adjacent guide `members 23 and through some of the openings 44 adjacent those areas. Tha-t rod will break away the portions 46 of reduced diameter-with consequent enlargement of the openings 44 and with consequent increased air dow. Two complete openings 44- and parts of five openings 44 which have had the portions 46 of reduced diameter broken away are shown at the left of FIG. 3.

The air diffusing member 42. -co-uld be made of different material-s, and the conliguratons ofthe openings 44 could be varied. However, since the air diff-using member 4Z is presently being marketed as a translucent plastic mask :for light sources, it is inexpensive and convenient to use that member in its marketed form.

Whereas the drawing and accompanying description `have shown and described a preferred embodiment or the present invention, it should be apparent to those skilled in the art that various changes may be made in the form of the invention without aiiecting the scope thereof.

What I claim is:

1. In a device for establishing and maintaining an air screen adjacent a doorway which comprises:

(a) a plenum chamber with an outlet opening adjacent one side of said doorway,

(b) an air intake opening adjacent the opposite side ot said doorway,

(c) an air discharge assembly adjacent said outlet opening or said plenum chamber which has a plurality of air-guiding members that are spaced apart to permit air to pass between them and which can apply laterally-directed components of motion to said air` to torce said `air to issue from said air discharge assembly at an angle to said outlet opening of said plenum chamber,

(d) a return air duct which 'can conduct air from said lair intake chamber to said plenum chamber,

(e) an Eairrnoving device that can draw air into said air intake chamber, can move said air through said return air duct to said plenum chamber, and can cause said air to pass outwardly through said air discharge assembly and across said doorway to said air intake chamber, and

(f) an air diffusing member,

(g) said .air d-iiiusing member being mounted immediately adjacent the inlet face of said air discharge assembly,

(h) said air diffusing member having a large number of openings therethrough with large inlets and large outlets and reduced diameter portions intermediate said inlets and outlets to provide said openings with venturi-like coniigurations,

i (i) said openings causing passing therethrough to experience an initial increase in density and velocity andan initial decrease in volume `and then subsequently to experience an increase in volume and a reduction in density and a reduction in velocity as it issues from said diffusing member and passes to said air discharge assembly,

(j) whereby said air will be substantially free oi turbulence and ot laterally-directed components of motion as it enters said discharge assembly so said aireguiding members can effectively force said air to issue from said air discharge assembly aft an angle to said outlet opening `off said plenum chamber,

(k) said air diiiusing member resting upon and being connected to some or said air-guiding members oi said -air discharge assembly whereby said air dilusing member is movable with the inlet face of said air discharge assembly,

(1) said air diffusing member substantially preventing llutter in said air discharge assembly.

2. In a device for establishing tand maintaining an air screen adjacent a doorway which comprises:

(a) a plenum chamber with -an outlet opening adjacent one side ot said doorway,

(b) an air intake opening adjacent the opposite side of said doorway,

(c) an air discharge assembly adjacent said outlet opening o f said plenum chamber which has a plurality of air-guiding members that are spaced apart to permit air to pass between them and which can apply laterally-directed components of motion to said air to force said -to issue from said air discharge assembly at an angle to said outlet opening or said plenum chamber,

(d) a return air duct which can conduct air from said @air intake chamber to said plenum chamber,

(e) an air-moving device that can draw air into said air intake chamber, can move said air through said return air duct to said plenum chamber, and can cause said air to pass outwardly through said air discharge assembly and across said doorway to said air intake chamber, and

(f) an air diiusing member,

(g) said .air diffusing member being mounted immediately adjacent the inlet face of said air discharge assembly,

(h) said air dillusing member having a large number of openings therethrough with large inlets and large outlets and reduced diameter portions intermediate said inlets and outlets to provide said openings with venturi-like configurations,

(i) said openings causing air passing therethrough to experience an initial increase in density and velocity and an initial decrease in volume and then subsequently to experience an increase in volume and a reduction in density and a reduction in velocity as it issues from said air diiusing member and passing ito said air discharge assembly,

(j) Whe-roby said air will Ibe substantially tre-e of turbulence and of laterally-directed components of motion as it enters said air discharge assembly so said air-guiding members can effectively force said air to issue -from said air discharge assembly at an angle to said outlet opening or said plenum chamber.

3. In a device for establishing and maintaining an air screen adjacent a doorway which comprises:

(a) ya plenum chamber with -an outlet opening adjacent one side of said doorway,

(b) an air intake opening adjacent the opposite side of said doorway,

(c) an air discharge assembly adjacent said outlet opening of said plenum chamber which has a plurality of air-guiding members that are spaced apart to permit air to pass between them and which can apply laterally-directed components of motion to said air to force said air to issue from said air discharge assembly at an angle to said outlet opening of said plenum chamber, v

(d) a return duct which can conduct air from said air intake chamber to said plenum chamber,

(e) an air-moving device that can draw air into said air intake chamber, can Ixn-ove said air through said return air duct to said plenum chamber, and can cause said air to pass outwardly through said air discharge assembly land across said doorway to said air intake chamber, and

(f) an lair diffusing member,

(g) said air diffusing member being mounted ahead of the inlet face of said air discharge assembly,

(h) said air diusing member having a large number of openings therethrough with large inlets and large outlets and reduced area portions intermediate said inlets and outlets,

(i) said air diffusing member resting upon the leading edges of said air-guiding members and being secured to some of said air-guiding members whereby saidair diffusing member is movable with the inlet face of said air discharge assembly,

`(j) the engagement of said air diffusing member with said leading edges of said air-guiding members substantially preventing flutter in said Iair discharge assembly.

4. In a device 'for establishing and maintaining 'an air screen adjacent a doorway which comprises:

1 (a) a plenum chamber with au outlet opening adjacent one side of said doorway,

(b) an air intake opening adjacent the opposite side of said doorway,

(1c) an air discharge assembly adjacent said outlet opening of said plenum chamber which has a plurality of air-guiding members that are spaced apart to permit air to pass between them and which can apply laterally-directed components off motion to said air to torce said air to issue from said air discharge assembly at an angle `to said outlet opening of said plenum chamber,

(d) a return air duct which can conduct air from said 'air intake chamber to said plenum chamber,

(e) an air-moving device that can draw air into said `air intake chamber, can move said air through ysaid return air duct Ato said plenum chamber, 'and can cause said air to pass outwardly through said air discharge assembly and across said doorway to said air intake chamber, and

(f) an air diffusing member,

` '(g) said lair diffusi-ng member being mounted ahead of the inlet ace'off said air discharge assembly,

(h) said air diffusing member having a large number of openings with large inlets and large outlets and reduced area portions intermediate said inlets and outlets .which cau-se air passing therethrough to experience an initial increase in density and velocity and an initial decrease in volume and then subsevquently to experience an increase in volume and a reduction in density and a reduction in velocity a-s it issues from said air diffusing member and passes to -said air discharge assembly.

5. In a device for establishing and maintaining an air screen adjacent a doorway which comprises:

(a) a plenum chamber with an outlet opening adjacentA one side of said doorway,

(b) an air intake opening adjacent the opposite side of said doorway,

(c) an air discharge assembly adjacent said outlet opening or" said plenum chamber which has a plurality of air-guiding members that are spaced apart 'to permit air to pass between them and which can apply laterally-directed components of motion to said air lto torce said air 'to issue 4from said air discharge assembly at an angle to said outlet opening of said plenum chamber,

(d) a return air duct which can conduct air from said air intake Ichamber to said plenum chamber,

(e) an air-moving device that `can draw air into said lair intake chamber, can move said air through said return air duct fto said plenum chamber, and can cause said air lto pass outwardly through said air discharge assembly land across said doorway to said air f .intake chamber, and

(f) an air diffusing member,

(g) said air diffusing member being mounted immediately adjacent the inlet tace of said air discharge assembly,

' .(h) said air diffusing member having a large number of openings therethrough with large inlets and large outlets and reduced diameter portions -intenmediate said inlets and outlets to provide said openings with .venturi-like configurations.

6. vIn a device for establishing and maintaining an air screenadjacent a doorway which comprises:

(a) 'a plenum chamber with an outlet opening adjacent `one side of said doorway,

(b) an air discharge assembly |adjacent said outlet opening or" said plenum chamber which has a plurality of air-guiding members that are spaced apart to ,permit air to pass between them and wh-ich can apply laterally-directed components of motion to said air lto force said air to issue from said air discharge 'assembly at an angle to said outlet opening of said plenum chamber,

(c) an air-moving device that can ycause air .to pass out-v wardly through said discharge assembly, and

(d) an lair diffusing member,

(e) said air diffusing member being mounted immediately adjacent the inlet face of said air discharge assembly,

(f) said Iair diffusing member having a large number of openings therethrough with large inlets and large outlets and reduced diameter portions intermediate said inlets and outlets to provide said opening-s with venturi-like configurations,

(g) said openings causing air passing therethrough to experience an initial increase in density and velocity and an initial decrease in volume and then subsequently to experience an increase in volume and a reduction in density and a reduction in Velocity as it issues from said air diffusing member and passes to said air discharge assembly,

(h) whereby lsaid air will be substantially free of turbulence and of laterally-directed components or motion as it enters said .air discharge assembly.

7. In -a device for establishing and main-taining an air screen adjacent a doorway which comprises:

.(a) aplenum chamber with an outlet Opening adjacent one side of said doorway,

(b) an air discharge assembly adjacent said outlet opening of said plenum chamber which has a plurality of air-guiding members that are spa-ced apart to permit air to pass between Ithem and which can `apply `laterally-directed components of motion to said air to torce said air to issue y'from said air discharge Iassembly at an angle to said outlet opening of said j plenum chamber,

(c) an airemoving device that can cause air to pass outlwardly through said discharge assembly, and

(d) an air diffusing member,

(e) said air diffusing member having a large number of openings therethrough with venturi-like configurations,

(-f) said openings in said air diffusing member having large inlets and large `outlets and portions of reduced diameter intermediate said inlets and outlets,

(g) said portions of reduced diameter being readily broken to enlarge said openings in said air diffusing Lmembers, Iand thereby increase the flow of air through said openings,

(h) said air diffu-sing member being mounted inwardly of said air discharge assembly,

(i) said openings causing air passing therethrough to experience ran initial increase in density and velocity and an initial `decrease in volume and then subsequently to experience an increase in volume and a reduction in density and a Ireduction in velocity as it issues from said air diffusing member and passes to lsaid air discharge assembly.

S. In a device for establishing and maintaining an air screen adjacent a doorway which comprises:

(c) an air-moving device that can `cause air to parss out- Wardly through said air discharge assembly, and

(d) `an air diffusing member,

(e) `said -air diffusing member having a large number of openings ltherethrough with venturi-like configurations,

(f) said openings in said air diffus-ing member having large inlets and large outlets and portions of reduced diameter intermediate said inlets and outlets,

(g) said portions of reduced diameter being readily broken to enlarge said yopenings in said air diffusing members, and thereby increase the ow of air through said openings.

References Cited by the Examiner 5 UNITED STATES PATENTS 3,021,776 2/1962 Kennedy y98--36 X 3,113,501 12/1963 Cargo 98-36 WILLIAM F. ODEA, Acting Primary Examiner. 10 JOHN F. OCONNOR, Examiner. 

1. IN A DEVICE FOR ESTABLISHING AND MAINTAINING AN AIR SCREEN ADJACENT A DOORWAY WHICH COMPRISES: (A) A PLENUM CHAMBER WITH AN OUTLET OPENING ADJACENT ONE SIDE OF SAID DOORWAY, (B) AN AIR INTAKE OPENING ADJACENT THE OPPOSITE SIDE OF SAID DOORWAY, (C) AN AIR DISCHARGE ASSEMBLY ADJACENT SAID OUTLET OPENING OF SAID PLENUM CHAMBER WHICH HAS A PLURALITY OF AIR-GUIDING MEMBERS THAT ARE SPACED APART TO PERMIT AIR TO PASS BETWEEN THEM AND WHICH CAN APPLY LATERALLY-DIRECTED COMPONENTS OF MOTION TO SAID AIR TO FORCE SAID AIR TO ISSUE FROM SAID AIR DISCHARGE ASSEMBLY AT AN ANGLE TO SAID OUTLET OPENING OF SAID PLENUM CHAMBER, (D) A RETURN AIR DUCT WHICH CAN CONDUCT AIR FROM SAID AIR INTAKE CHAMBER TO SAID PLENUM CHAMBER, (E) AN AIR-MOVING DEVICE THAT CAN DRAW AIR INTO SAID AIR INTAKE CHAMBER, CAN MOVE SAID AIR THROUGH SAID RETURN AIR DUCT TO SAID PLENUM CHAMBER, AND CAN CAUSE SAID AIR TO PASS OUTWARDLY THROUGH SAID AIR DISCHARGE ASSEMBLY AND ACROSS SAID DOORWAY TO SAID AIR INTAKE CHAMBER, AND (F) AN AIR DIFFUSING MEMBER, (G) SAID AIR DIFFUSING MEMBER BEING MOUNTED IMMEDIATELY ADJACENT THE INLET FACE OF SAID AIR DISCHARGE ASSEMBLY, (H) SAID AIR DIFFUSING MEMBER HAVING A LARGE MEMBER OF OPENINGS THERETHROUGH WITH LARGE INLETS AND LARGE OUTLETS AND REDUCED DIAMETER PORTIONS INTERMEDIATE SAID INLETS AND OUTLETS TO PROVIDE SAID OPENINGS WITH VENTURI-LIKE CONFIGURATIONS, (I) SAID OPENINGS CAUSING AIR PASSING THERETHROUGH TO EXPERIENCE AN INITIAL INCREASE IN DENSITY AND VELOCITY AND AN INITIAL DECREASE IN VOLUME AND THEN SUBSEQUENTLY TO EXPERIENCE AN INCREASE IN VOLUME AND A REDUCTION IN DENSITY AND A REDUCTION IN VELOCITY AS IT ISSUES FROM SAID AIR DIFFUSING MEMBER AND PASSES TO SAID AIR DISCHARGE ASSEMBLY, (J) WHEREBY SAID AIR WILL BE SUBSTANTIALLY FREE OF TURBULENCE AND OF LATERALLY-DIRECTED COMPONENTS OF MOTION AS IT ENTERS SAID AIR DISCHARGE ASSEMBLY SO SAID AIR-GUIDING MEMBERS CAN EFFECTIVELY FORCE SAID AIR TO ISSUE FROM SAID AIR DISCHARGE ASSEMBLY AT AN ANGLE TO SAID OUTLET OPENING OF SAID PLENUM CHAMBER, (K) SAID AIR DIFFUSING MEMBER RESTING UPON AND BEING CONNECTED TO SOME OF SAID AIR-GUIDING MEMBERS OF SAID AIR DISCHARGE ASSEMBLY WHEREBY SAID AIR DIFFUSING MEMBER IS MOVABLE WITH THE INLET FACE OF SAID AIR DISCHARGE ASSEMBLY, (L) SAID AIR DIFFUSING MEMBER SUBSTANTIALLY PREVENTING "FLUTTER" IN SAID AIR DISCHARGE ASSEMBLY. 